Thin film formation by sputtering using a magnet, for example, magnetron sputtering, is capable of providing high-quality film and implementing high-speed film formation and therefore has been put into practical use in various fields. Manufacturing of semiconductor devices and electronic components is not exception, and the sputtering using a magnet is considered as an important technique influencing the characteristics of the devices and the like. In recent years, the semiconductor devices and electronic components have been rapidly increasingly sophisticated and highly integrated (made finer), and more exacting requirements have been imposed for quality of thin film, forming conditions, and the like. For example, sputtering has been required to form thin film with high quality (low resistance) on semiconductor substrates in the process of deposition. As an example of such sputtering apparatuses, an apparatus shown in Patent Document 1 has been proposed, for example.
In the case of thin film formation on a substrate by sputtering, the vacuum vessel is temporarily exposed to the atmosphere at periodic maintenance or the like, and in this case, an oxidized layer and the like are formed on the surface of the target. Moreover, when continuous deposition for a long total deposition time is performed, a re-deposited film of a target material adheres to a region with small erosion on the target surface (in other words, a region of the target surface having a low sputtering rate) in some cases. When thin film is formed without the above surface oxidized layer sufficiently removed, or when the film is formed while there remains the re-deposited film of the target material formed on the target surface due to the continuous film formation, the thin film formed on the substrate has a high specific resistance. Accordingly, thin film with good film quality cannot be formed, and there are problems including functional degradation of devices and reduction in yield. In order to form highly-sophisticated thin film, it is important to prepare a proper surface state of the target by performing adequate sputter cleaning.
An example of such sputter cleaning is a method shown in Patent Document 2. The example shown in Patent Document 2 discloses a technique of weakening a magnetic field formed on the target surface when performing target cleaning, thereby cleaning the entire surface of the target even when the entire surface is oxidized
Furthermore, an example of conventional sputter cleaning apparatuses is described based on FIG. 17 (Patent Document 3). In FIG. 17, reference numeral 101 indicates a vacuum chamber; 102, a substrate holder; 103, a substrate; 104, an electrode; 105, a target; 106, a high-voltage power supply; 107, an ammeter; 108, a voltmeter; 109, a controller; 110, a power supply switch; and 111, a shutter. At main sputtering (deposition on the substrate) of the apparatus of FIG. 17, when the switch 110 is turned on, ions in plasma collide with the target 105 as a cathode, and atoms of the target 105 are ejected. These ejected atoms adhere to the substrate 103 to form film.
In the case of performing pre-sputtering (cleaning of the target surface) before the main sputtering, a dummy substrate 103 for pre-sputtering is attached to the substrate holder 102 (step S1), and first discharge (pre-sputtering 1) is performed only for a predetermined period of time. Next, second discharge (pre-sputtering 2) is performed (step S3). In this pre-sputtering 2, discharge is performed at higher power than the pre-sputtering 1. During the second discharge, the value of current flowing between the target 105 and dummy substrate 103 or the value of voltage across the same is measured at predetermined time intervals, and the measured values are monitored. Next, it is determined whether the monitored values of current or voltage are stabilized, that is, whether the value previously monitored is equal to the value currently monitored (step S5). When the currently monitored value of current or voltage is not equal to the value previously monitored, the discharge is continued, or otherwise, the discharge is stopped.